(1) Field of the Invention
The present invention relates to a nozzle plate production method and an apparatus for the same which produces a nozzle plate of an ink-jet head of an ink-jet printer.
Ink discharge characteristics of an ink-jet head of an ink-jet printer affect the quality of a printed image produced by the ink-jet head on a sheet of paper. The ink discharge characteristics are affected by the shape of a nozzle hole of a nozzle plate of the ink-jet head. When it is desired to produce a nozzle plate for an ink-jet head which provides a high quality printed image on the sheet of paper, the shape of the nozzle hole of the nozzle plate is an important factor to consider.
Generally, a large number of small nozzle holes with a given pitch are formed in the nozzle plate of the ink-jet head. It is a difficult task to accurately produce the nozzle plate so as to enable the ink-jet head to provide a high quality printed image, and the cost is likely to be increased. It is therefore desired to provide a nozzle plate production method, and an apparatus for the same, which is capable of easily and accurately producing the nozzle plate with a reduced cost.
(2) Description of the Related Art
Japanese Laid-Open Patent Application No. 7-60971 discloses a conventional nozzle plate of an ink-jet head. FIG. 1 shows a nozzle plate 10 of a piezoelectric ink-jet head disclosed in the above-mentioned publication.
As shown in FIG. 1, the nozzle plate 10 includes a nozzle hole 11. The nozzle hole 11 has a tapered portion 12 on the side of an upper end surface and a straight cylindrical portion 14 on the side of a lower end surface. The tapered portion 12 of the nozzle hole 11 is open to an ink chamber (not shown) of the ink-jet head. The cylindrical portion 14 extends from a bottom edge of the tapered portion 12. The cylindrical portion 14 includes an ink discharge opening 13 from which ink is discharged. In the nozzle plate 10 of the above-mentioned publication, a ridge 15 is formed between the bottom edge of the tapered portion 12 and an upper edge of the cylindrical portion 14.
FIGS. 2A, 2B and 2C show basic processes of a nozzle plate production method disclosed in the above-mentioned publication.
The nozzle hole 11 of the nozzle plate 10 is formed through the nozzle plate production method of FIGS. 2A, 2B and 2C. The tapered portion 12 of the nozzle hole 11 is formed by performing a punching process of FIG. 2A. When the punching process of FIG. 2A is performed, a nib 16 is produced on the bottom of the nozzle plate at the nozzle hole 11. The nib 16 is removed from the nozzle plate by performing a grinding process of FIG. 2B. The cylindrical portion 14 of the nozzle hole 11 is formed by performing a reaming process of FIG. 2C. When the reaming process of FIG. 2C is performed, a burr is produced in the nozzle hole 11. A grinding step is performed to remove the burr from the nozzle hole 11. The nozzle plate 10 of FIG. 1 is thus produced.
In the nozzle plate 10 of the above-mentioned publication, the ridge 15 has a sharp edge and a cross-sectional area of the nozzle hole 11 from the tapered portion 12 to the cylindrical portion 14 does not smoothly change. Therefore, the motion of the meniscus of the ink within the nozzle hole 11 when the ink is discharged from the nozzle hole 11 becomes noncontinuous and unstable, and the ink discharge characteristics of the ink-jet head are degraded.
It is difficult for the ink-jet head having the nozzle plate 10 of the above-mentioned publication to provide a high quality printed image because the ink discharge characteristics of the ink-jet head are low. Further, the nozzle plate production method of producing the nozzle plate 10 of the above-mentioned publication requires both the punching step and the reaming step be accurately performed to form the nozzle hole 11, and it is difficult to reduce the cost for the production of the nozzle plate 10.